Wind storms, Gust Fronts &
Outflow

Gust Front Storms With
Rotation - Tricky Business

This severe storm in northeast Colorado was producing a gust
front and rotating at the same time. Note the cyclonic banding above the
outflow on the left side of the image (west) where the storm is approaching. An
old cell to the east is providing and outflow boundary for the storm to ride
along. It never produced a tornado, but storms that have both these features of
rotation, and strong straight line winds can cause considerable property
damage.

Atmospheric conditions did support a tonado out of another
storm about 40 mile south of this cell an hour later. The image was taken near
Akron, Colorado.

Gust Front Appearance in a
Rotating Supercell

The storm pictured here on first glance would appear to be a gust
front storm but looks are deciving. Not the small tree on the east side of the
small town (or just left of center). It's leaning over to the west as strong
winds feed into the storm. The shelf appearance does not guarantee the storm is
a gust front producer or in an outflow stage. In this particular case the storm
produced a confirmed tornado with F-2 damage about an hour and a half after
this picture was taken. After dark, I watch with a group of chasers as an
elephant trunk tornado formed about a mile west of our position, but we were
unable to capture it in the lightning.

Severe Colorado Hail and Wind Storm that is
not Rotating

A Colorado storm is pictured here that moved northeast into far
southwestern Nebraska. It looks somewhat similar to the previous storm, but is
not rotating and blasted us with strong straight winds and hail. If you see a
storm like this watch the motion on the top of the shelf cloud. Is it pushing
out, or rotating back into the storm? This one was pushing out. Also, watch in
wind direction under the leading edge to see if the storm has inflow like the
two pictured above or winds are gusting our and away from the
storm.

Squall Line with a Stacked
Shelf Cloud

Vehicles rush to beat the storms approaching from the north. This is
an example of a typical squall line with strong straight line winds, heavy rain
and hail. The leading edge of the clouds brings a cold wind shift coming out of
the storm. The cold air works like a shovel scooping up moisture and forming
new convection and storms on the leading edge of the
outflow.

Severe Colorado Hail and Wind
Storm

This storm produced high winds on the leading edge of the gust front
and then battered homes with large hail. The clouds on this outflow boundary
were horizontally turning over as it rushed out to the east. The temperature
dropped dramatically, which is usually the case during summer thunderstorms on
the high plains.

Strong Straight Line Winds and a Dangerous
Gustnado

This storm produced straight line wind over 80 m.p.h. and caused
considerable property damage in rural sections of north central Oklahoma. This
was part of a line of storms producing widespread high wind over a large of
northern Oklahoma. The cloud base was quite high, about 7,000 feet above ground
level, and the large cloud of dust is over 3,000 feet high and a quarter mile
wide at the bottom. It was rotating violently, and produced an audible roar
that could be heard for about 2 miles. This (straight line) wind driven "spin
up" lasted for over 10 minutes while I drove toward it and another 5 minutes
after I got in front of it. It was in the earlier days of my chasing and I had
no idea how powerful such a vortex could be. The circulation propagated along
at the speed of the outflow, but was rotating faster than the surrounding
winds. When I heard the loud roar and saw trees and shrubs flying apart I made
a hasty retreat. Circulations such as this must be rare and this is the only
one I have witnessed. As a tornado, I estimate it would be only rated at F-1
which is weak, but certainly a storm that demands respect. More commonly
gustnadoes are smaller and short lived. On days when conditions are correct
multiple gustnados
may occur. These gustnados did have a circulation at cloud
base.

Monster Gust
Front

A cranked up gust front roaring across the countryside. This is known
as an arcus-gust front. Note the arc shape to the outflow and the dust being
carried into the air. These storm can move at 60 plus m.p.h. and usually
deliver more dirt that rain since the precipitation area is narrow and it moves
by fast. Tornadoes get the headlines, but these storms can create wide spread
damage.